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<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>get(5) 传入 5 计算出 5，传入 6 计算出 8，传入几就算出第几位数</title>
</head>

<body>
  <script>
    function recursion(n) {
      if (n < 0) {
        return '输入的数字不能小于0'
      } else if (n == 0) {
        return 0
      } else if (n == 1) {
        return 1
      } else if (n > 1) {
        return recursion(n - 1) + recursion(n - 2)
      }
    }
    console.log(recursion(6))
  </script>
</body>

</html>